UNI/TH

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2019-05-13
14:55
OpenAccess [PUBDB-2019-02239] Report/Journal Article
et al
Conformal symmetry of QCD in d-dimensions
[DESY-18-175; arXiv:1810.04993]
QCD in $d=4-2\epsilon$ space-time dimensions possesses a nontrivial critical point. Scale invariance usually implies conformal symmetry so that there are good reasons to expect that QCD at the critical point restricted to the gauge invariant subsector provides one with an example of a conformal field theory. [...]
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2019-04-15
11:51
OpenAccess [PUBDB-2019-01952] Report/Journal Article
et al
Two-loop evolution equations for flavor-singlet light-ray operators
[arXiv:1901.06172; DESY-18-202]
QCD in non-integer $d=4-2\epsilon$ space-time dimensions enjoys conformal invariance at the special fine-tuned value of the coupling. Counterterms for composite operators in minimal subtraction schemes do not depend on $\epsilon$ by construction, and therefore the renormalization group equations for composite operators in physical (integer) dimensions inherit conformal symmetry. [...]
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2019-03-22
09:15
OpenAccess [PUBDB-2019-01665] Report/Journal Article

$b$-hadron production in the general-mass variable-flavor-number scheme and the LHC data
[arXiv:1809.04297; DESY-18-154; MITP-18-085]
We study inclusive $b$-hadron production in $pp$ collisions at the LHC at different center-of-mass energies and compare with experimental data from the LHCb and CMS collaborations. Our predictions for cross sections differential in the transverse momentum and (pseudo)rapidity agree with data within uncertainties due to renormalization scale variations [...]
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2019-03-14
13:47
arXiv [PUBDB-2019-01539] Report/Journal Article

$\Lambda_b^0$-baryon production in pp collisions in the general-mass variable-flavour-number scheme and comparison with CMS and LHCb data
[DESY-18-036; arXiv:1803.11103; MITP-18-020]
We calculate the next-to-leading-order cross section for the inclusive production of $\Lambda_b$ baryons in pp collisions in the general-mass variable-flavor-number scheme. We use realistic evolved non-perturbative fragmentation functions obtained from fits to B-meson production in $e^+ e^-$ annihilation and compare our results for transverse-momentum and rapidity distributions with recent experimental data from the CMS and the LHCb collaborations at the CERN LHC. [...]
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2019-02-18
15:45
OpenAccess [PUBDB-2019-01145] Report/Journal Article

Integrability in heavy quark effective theory
[arXiv:1804.06289; DESY-18-056]
It was found that renormalization group equations in the heavy-quark e ectivetheory (HQET) for the operators involving one e ective heavy quark and light degrees offreedom are completely integrable in some cases and are related to spin chain models withthe Hamiltonian commuting with the nondiagonal entry C(u) of the monodromy matrix.In this work we provide a more complete mathematical treatment of such spin chains inthe QISM framework. We also discuss the relation of integrable models that appear in the HQET context with the large-spin limit of integrable models in QCD with light quarks. [...]
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2019-02-18
12:04
OpenAccess [PUBDB-2019-01141] Preprint/Report
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Five-loop contributions to low-N non-singlet anomalous dimensions in QCD
[arXiv:1812.11818; Nikhef-2018-066; DESY-18-227; LTH-1191]
 GO
We present the first calculations of next-to-next-to-next-to-next-to-leading order (N 4 LO) contributions to anomalous dimensions of spin- N twist-2 operators in perturbative QCD. Specifically, we have obtained the respective non-singlet quark–quark anomalous dimensions at N=2 and N=3 to the fifth order in the strong coupling αs . [...]
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2019-01-28
13:28
OpenAccess [PUBDB-2019-00784] Preprint/Report
et al
Two-loop evolution equations for flavor-singlet light-ray operators
[arXiv:1901.06172; DESY-18-202]
QCD in non-integer $d=4-2\epsilon$ space-time dimensions enjoys conformal invariance at the special fine-tuned value of the coupling. Counterterms for composite operators in minimal subtraction schemes do not depend on $\epsilon$ by construction, and therefore the renormalization group equations for composite operators in physical (integer) dimensions inherit conformal symmetry. [...]
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2018-12-13
15:06
OpenAccess [PUBDB-2018-05453] Report/Journal Article

Three-loop effective potential of general scalar theory via differential equations
[arXiv:1810.07476; DESY 18-173; DESY-18-173]
We consider the scalar sector of a general renormalizable theory and evaluate the effective potential through three loops analytically. We encounter three-loop vacuum bubble diagrams with up to two masses and six lines, which we solve using differential equations transformed into the favorable ϵ form of dimensional regularization. [...]
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2018-11-19
13:52
OpenAccess [PUBDB-2018-04610] Report/Journal Article

Operator mixing in fermionic CFTs in noninteger dimensions
[arXiv:1809.00021; DESY-18-149]
We consider the renormalization of four-fermion operators in the critical QED and SU(Nc) version of the Gross-Neveu-Yukawa model in noninteger dimensions. Since the number of mixing operators is infinite, the diagonalization of an anomalous dimension matrix becomes a nontrivial problem. [...]
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2018-11-05
13:50
OpenAccess [PUBDB-2018-04145] Report/Journal Article

Breakdown of Nonrelativistic QCD Factorization in Processes Involving Two Quarkonia and its Cure
[arXiv:1809.07993; DESY-18-168]
We study inclusive processes involving two heavy quarkonia in nonrelativisitic QCD (NRQCD) and demonstrate that, in the presence of two P-wave Fock states, NRQCD factorization breaks down, leaving uncanceled infrared singularities. As phenomenologically important examples, we consider the decay $\Upsilon \to \chi_{cJ}+X$ via $b\bar{b}({}^3P_{J_b}^{[8]})\to c\bar{c}({}^3P_J^{[1]})+gg$ and the production process $e^+e^-\to J/\psi+\chi_{cJ}+X$ via $e^{+}e^{-}\to c\bar{c}({}^3P_{J_1}^{[8]})+c\bar{c}({}^3P_J^{[1]})+g$. [...]
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